1. Field of the Invention
The present invention relates to a twist beam suspension consisting of a twist beam which is disposed so as to extend in the transverse direction of a vehicle, and a pair of trailing arms which are disposed at longitudinal ends of the twist beam so as to extend in the longitudinal direction of the vehicle.
2. Description of the Related Art
FIG. 7 shows a plan view of a twist beam rear suspension. An example of such a twist beam rear suspension is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 4-283114.
As shown in FIG. 7, such a twist beam rear suspension consists of a twist beam 100 which has an open (i.e., substantially C-shaped) cross-sectional configuration and which is disposed so as to extend in the transverse direction of a vehicle, and a pair of trailing arms 102 and 104 disposed at longitudinal ends of the twist beam 100 so as to extend in the longitudinal direction of the vehicle.
From the rear ends of these trailing arms 102 and 104 are projected spindles 106 and 108, by which unillustrated right and left wheels are rotatably supported. Further, bushes 110, 112, whose axial directions run along the transverse direction of the vehicle, are press-fit to the vehicle longitudinal direction front end portions of the trailing arms 102, 104, respectively.
FIG. 8 shows an enlarged view of the bush 110 located on the right side in FIG. 7. As shown in FIG. 8, the bush 110 is composed of a cylindrical inner tube 114, a cylindrical outer tube 116 disposed so as to be apart from the out peripheral portion of the inner tube 114, and a rubber member 118 adhered by vulcanization between the inner tube 114 and the outer tube 116. On the inner side of the inner tube 114 in the transverse direction of the vehicle, an inner-side bracket 120 is mounted to a vehicle body such that the bracket 120 abuts the inner end of the inner tube 114. Similarly, on the outer side of the inner tube 114 in the transverse direction of the vehicle, an outer-side bracket 122 is mounted to the vehicle body such that the bracket 122 abuts the outer end of the inner tube 114. In this state, a bolt 124 is inserted into the inner tube 114 after passing through the outer-side bracket 122, and a nut 126 is screwed onto the bolt 124, whereby the trailing arm 102 is swingably connected to the vehicle body. The bush 112 on the left side in FIG. 7 has the same structure.
In the above-described twist beam rear suspension, the distance A' between the inner end of the outer tube 116 and the outside surface of the inner-side bracket 120 is designed to be substantially equal to the distance B' between the outer end of the outer tube 116 and the inner side surface of the outer-side bracket 122. In some cases, the distance A' becomes larger than the distance B', because of the conditions of assembly and the like. Therefore, the conventional twist beam rear suspension has a drawback that the twist beam 100 receives a compression force when an excessive lateral force acts on one of the wheels.
That is, when an excessive lateral force F' acts leftward on the right wheel as shown in FIG. 7, the entire rear suspension tends to move leftward in FIG. 7 due to the lateral force F'. As described above, if the distance A' is stated larger than the distance B', the outer end of the outer tube 116 of the left-side bush 112 abuts the outer-side bracket 122 before the inner end of the outer tube 116 of the right-side bush 110 abuts the inner-side bracket 120. Therefore, the lateral force F' is transmitted to the vehicle body via the right-side trailing arm 102, the twist beam 100, the left-side trailing arm 104, the outer tube of the left-side bush 112 and the outer-side bracket 122 located on the left side of the twist beam 100. At this time, the twist beam 100 is subjected to the leftward lateral force F' and a reaction force which is transmitted from the outer-side bracket 122 located on the left side of the twist beams 100 to the outer tube of the left-side bush 112 (i.e., the left-side trailing arm 104). Accordingly, a compression force acts on the twist beam 100. This compression force as well as the open cross-sectional configuration of the twist beam 100 adversely affects the strength of the twist beam 100.